In a 3G system, roaming handovers are an important part in mobility management. Due to mobility of the multimode user equipment (UE), its connection service is handed over from one cell to another so that the network can ensure users good service, reduce call-drop rate, improve speech quality and reduce network congestion.
When in connection mode, the multimode user equipment leaves a wireless access system and enters into another wireless access system, during the course of handover, user service is still maintained, and this process is referred to as intersystem handovers. When in other modes other than connection, the multimode user equipment leaves a wireless access system for another, roaming process happens. Then the multimode user equipment can gain access to a new system for service at a new place. The aim for intersystem handovers is to provide mobile subscribers better quality of service at bordering areas between different systems.
Because the present networks are mainly 2G networks, which can not be possibly updated to 3G networks all at once, 3G networks and 2G networks will certainly coexist for a rather long period. Therefore, it is very important to realize the function of roaming handovers between 3G networks and 2G networks.
When 3G networks become poor in coverage, if there is good 2G coverage in this area, 3G networks will control the multimode user equipment and order it to start measuring 2G networks. If 2G networks' quality meets the requirement, the multimode user equipment will send corresponding measurement reports to 3G networks which, after judging the reports, will initiate a handover to 2G networks, thus maintaining the conversation process.
In connection mode, when 3G networks control the multimode user equipment and order it to measure 2G networks' signals, the 2G network neighbor lists need to be delivered to the multimode user equipment. If the 2G network neighbor lists are not configured, or the target 2G cell's neighbors are not configured in the lists, the multimode user equipment cannot implement the handover, thus causing a call-drop. Whereas in idle mode, the multimode user equipment will reselect a 2G system based on the system-delivered 2G neighbor lists. If 2G networks' quality meets the requirement, the multimode user equipment will reselect 2G networks.
From the above explanations, whether the multimode user equipment is in connection mode or in idle mode, it needs to use the 2G neighbor lists to finish the handover or reselection.
In connection mode, if the 2G neighbor lists are miss-configured, when 3G coverage becomes poor, it can cause poor speech quality, discontinuity of conversation at the same time and maybe call dropping in serious conditions.
In idle mode, if the 2G neighbor lists are miss-configured, when 3G coverage becomes poor, it can cause network dropping, after which the multimode user equipment needs to spend a long time searching cells, meanwhile it cannot make or receive calls, which will seriously affect users' feelings.
Generally speaking, when a 3G network is formally put into operation, the system has already been configured with initial 2G neighbor lists, which may not be complete and need continuous optimization in future operation stage of the network. Through optimizing the 2G neighbor lists, it can improve the quality of handovers and reselections between 3G networks and 2G networks. The following method is commonly used for optimizing the lists of 3G and 2G neighbors:
1) analyzing users' complaints, and determining accordingly whether they are caused by handovers or reselections between 3G and 2G networks, and arranging specified tests;
2) analyzing certain cells' performance counter, examining the handover success rate index, and seeing if the indexes are very poor, if so, arranging specified tests for these cells;
3) based on the above analyses, for the problematic areas and key-coverage areas, for example, indoor coverage areas, arranging channel tests and call quality test (CQT), and arranging special channel testing personnel to test and analyze testing data;
4) analyzing channel testing data or CQT testing data, analyzing the handover success rate between 3G and 2G networks, and confirming whether they are caused by the miss-configuring of 2G neighbors;
5) adding more 2G neighbors, and carrying out further tests to make sure problems are solved.
The prior art finds miss-configured 2G neighbors all by post-analyses, and before successfully solving the problem of the miss-configured 2G neighbors, many users possibly have already experienced poor network quality, which affects their feelings and damages the reputation of the network operator.
With the prior art, special channel tests and CQT tests are needed to find and solve the problem of miss-configured neighbors, which involves a great deal of manpower and resources as well as investments.
When the equipment and maintenance of 2G networks are different from that of 3G networks, the maintenance personnel of the 3G networks may not be informed duly of the adjustment of the 2G networks, for example, when the 2G networks adjust their antennas, add more sites or repeaters, the handovers between 3G and 2G networks and the relations between neighbors will change, which, without timely adjusting of the relations between neighbors, will affect speech quality and further users' final feelings.
When 3G networks are adjusted alone, the neighbor configuration relations between 3G and 2G networks experience changes too. The common method is to find problems by channel tests. However, channel tests cannot traverse all the channels and solve all the miss-configurations of neighbors; therefore, neighbor optimization has to be resorted to after some operation time of the network.